Photographic emulsion containing pseudo-cyanine dyes



Patented Aug. 7, 1934 PHOTOGRAPHIC EMULSION CONTAINING PSEUDO-CYANINE DYES Leslie G. S; Brooker, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New York Application June 29, 1932, Serial No. 619,961

15 Claims.

This invention relates to photographic emulsions and more particularly to gelatino-silverhalide emulsions sensitized with a new class of dyes, namely, oxazolo, thiazolo, and selenazolo pseudo cyanines.

In my co-pending application No. 548,026, it is shown that photographic emulsions may be sensitized with neothiazolocarbocyanines, prepared from bases of the thiazole series and that photographic emulsions may also be sensitized with dyes of the pseudo-cyanine type arising from the same and related bases.

It is, therefore, among the objects of the present invention to prepare photographic emulsions sensitized with anew class of pseudo-cyanine dyes and photographic elements coated with such emulsions. Other objects will appear upon a further perusal of this specication.

I'he nomenclature adopted in the present application is based upon that already existing` in other divisions of cyanine dye chemistry and is also in agreement with that used in the copending application referred to above.`

The bases which are used in the present application conform to the general type:

where Y represents oxygen, sulfur or selenium. This gives the bases termed voxazoles, thiazoles or selenazoles respectively. A and B represent univalent atoms or groups such as hydrogen or aliphatic or aromatic groupings. The 4,5 carbon atoms are joined by an ethylenic linkage. The numbering of the molecule as shown follows a system in general usage. It is that used, for instance, in Richters Lexikon der Kohlenstoi Verbindungen.

Many Z-methylthiazoles are described in the chemical literature; 2,4-dimethyloxazole is described by Schuftan (Ben, 1895, 28, 3070) (see also Oesterreich, Ber., 1897, 30, 2254) and the 2-methylselenazoles are described and claimed in the copending 'application of Brooker and White, Serial No. 619,959, filed of even date herewith.

The general formula for a dye of the type described in this invention is as follows and the general names `proposed become- 1a1ky1aa1ky14B-5A (siin) azolapseudo-cyanine 'salt according as Y represents oxygen, sulfur or selenium respectively. R1 and R2 represent alkyl groups, which may be similar or dissimilar and X represents a suitable acidic radical as will be apparent hereinafter.

'I'he quinoline nucleus may unsubstituted.

A general method for the preparation of these pseudo-cyanine (or \//cyanine) dyes is to treat an alkyl quaternary salt of the heterocycllc base containing a reactive methyl group with an alkyl halide of a 2-halogeno-quinoline, especially a 2- iodoquinoline, using an alkali or other suitable base to effect the condensation. For instance caustic soda or caustic potash may be employed, the reaction being performed with one of the lower alcohols as solvent. Instead of the alkali, an organic base such as trlethylamine may be used, with an alcohol as solvent, or again another method is to treat the two quaternary salts described above with quinoline. In this case dye formation can be seen to be occurring even in the cold but it is convenient to carry out the reaction at an elevated temperature of C. or somewhat higher. Certain of these methods are also describedlin my copending application No. 659,629 led February 6, 1933 which treats of the preparation and use of the oxa-p-cyanines. The various methods are also illustrated by the examples given in this application.

It may be noted here that it is desirable to have the 2-iodoquinoline salts well pulverized for the reactions. 'Ihe other salts used should also be finely divided except where they are quite soluble in the solvent employed, in which case it is not especially necessary.

The parts mentioned in the examples are parts by weight.

Dealing more specically with the'inventlon, 2,4-dimethy1thiazole, for instance, may be converted into a quaternary salt by heating it with an alkyl halide or an alkyl ester of an aromatic sulfonic acid or a. dialkylsulfate. If methyl ptoluene-sulfonate be chosen, there results 2,4- dimethylthiazole metho-p-toluenesulfonate, as shown below- To prepare the dye, this salt may then be treated with the 2-iodoquinoline alkyl halide. If 2-iodoquinoline ethiodide be chosen for this step, and the condensation is brought about by the use be substituted or -formulated as follows- S. H-c5/ 1 The above dye is named 3,4dimethyl-1'ethyl thiazolo-xp-cyanine iodide. The dyes are usually isolated as the iodides, since these are in general much less soluble than, for instance, the corresponding p-toluenesulfonates, bromides or chlorides.

In place of the caustic alkali employed as above, a strong organic base, for instance triethylamine, may be used, a total of two molecular proportions of the triethylamine being employed for one molecular proportion of each of the two participating alkyl quaternary salts involved in the reaction. In this case also it is convenient to use one of the lower alcohols as solvent. Resulting from this reaction there is formed, in addition to the dye, salts of triethylamine comparable to the potassium salts formed in the above reaction.

If quinoline is employed in place of the ethyl alcoholic caustic potash, the reaction may be Written- The quinoline is conveniently employed in excess of the quantity indicated in the above reaction, and its function is then as a solvent as well as a participator in the reaction.

The foregoing will also illustrate the manner in which the reactions may occur when starting with an oxazole or a selenazole in place of a thiazole.

As before mentioned since the Z-methylselenazoles referred to herein are not described in the literature, a general method for their preparation will be given hereinafter, although -as before stated these are the joint invention of myself and Frank L. White and are fully described and claimed in copending application Serial No. 619,- 959 filed of even date herewith.

The Z-methylselenazoles are of the following general structure where A and B are univalent atoms or groups such as hydrogen, alkyl or aryl.

A general method of preparation of these new bases is as follows. A halogeno ketone or alde,

hyde of the type known generally as an alphahalogeno ketone or aldehyde is used. Examples of such compounds are given below:

(a) H.CO.CH2C1 Chloroacetaldehyde (b) CHsCOCHzCl Chloroacetone (c) CeHCOCHzBr Phenacylbrom'ide (d) CsHsCOCH(CH3)Br Bromopropiophenone The product of the above reaction is named 2,4-dimethylselenazole, and is a liquid having a boiling point of 56-58 C. at 17 mm. and has an odor almost indistinguishable from that of 2,4- dimethylthiazole. The numbering usedv for the nucleus is that in common usage for the related sulfur-containing bases, the thiazoles.

If phenacyl bromide is used, the product is 4- phenyl-2-methylselenazole which is a solid with a melting point of 63-64" C.

The following will serve to illustrate the reaction. In the preparation of 2,4-dimethylselenazole, 23 parts of chloroacetone were diluted somewhat with 8 parts of absolute ethyl alcohol, the whole warmed gently on a waterbath and 30 parts of freshly prepared selenoacetamide were added in several small portions with thorough shaking, each portion being allowed to react before the next was added. The whole was then heated at 100 for 15 minutes. The mass was cooled, shaken with 200 parts of water, the aqueous extract made strongly alkaline with caustic soda and the base extracted with ether. The ether layer was dried with anhydrous potassium carbonate, filtered, the solvent evaporated and the base distilled. The 2,4-dimethylselenazole distilled at 56-58" C. at 17 mm. It is a colorless liquidI with an odour almost indistinguishable from that of 2,4-dimethylthiazole.

The following examples illustrate the preparation of my new dyes:

EXAMPLE I 1 ,3,4-TrimethylorazoZo-p-cyanine iodide One part of 2,4-dimethyloxazole was heated with 1.9 parts of methyl p-toluenesulfonate for six hours at 100 C. during the course of which the 2,4-dimethyloxazole metho-p-toluenesulfonate solidified. This salt was crushed and heated with 4 parts of pulverized 2-iodoquinoline methiodide and 20 parts of quinoline at 130-150 C. for twelve minutes and then at 160 for ten minutes, with constant agitation. On cooling the dye separated and wask filtered off, washed and given two recrystallizations from methyl alcohol. The dye formed light brown crystals and gave an orange-yellow Solution in methyl alcohol.

EXAMPLE 3,4-Dimethyl-1 '-ethyZoazoZo-o-cyanine iodide One part of 2,4-dimethyloxazole was converted into the metho-p-toluenesulfonate using 1.9 parts of methyl p-toluenesulfonate as described in the preceding example. The salt was dissolved in 20 parts of hot absolute ethyl alcohol and 4.1 parts of 2iodoquinoline ethiodide added, the whole brought to boiling point and a solution of 2 parts of triethylamine in 6 parts of absolute ethyl alcohol added gradually with constant agitation. On refluxing again the dye separated out from the reaction mixture in yellow needles and reiiuxing was continued for minutes. The dye was subsequently removed and purified by washing followed by recrystallization from methyl alcohol. The color of the solution was orange yellow and the dye formed somewhat amber yellow needles.

EXAMPLEDI 4-Phen1fZ-3-methyl-1'-ethyloxazolo-p-cyanine iodide 1.6 parts of 4-phenyl-2-methyloxazole, made according to Bliimlein (Ben, 1884, 17, 2578, see

also Lewy, Ber., 1887, 20, 2576; Ber., 1888, 21, 924) ywere heated with 1.9 parts of methyl p-toluenesulfonate for 18 hours at 100. The crude quater- Inary salt was dissolved in parts of hot absolute lethyl alcohol, `4.1 parts of 2-iodoquinoline ethiodide added, the whole brought to boiling and 2 parts ot triethylamine, diluted with 8 parts of absolute ethyl alcohol, added in portions with shaking. The dye rapidly separated from the hot liquid and boiling under redux was continued for a further 10 minutes. 'I'he dye was removed, washed and crystallized vfrom methyl alcohol when it formed yellow needles which gave an Vorange-yellow solution.

EXAMPL: 1V

3-Meth1/l-1 '-ethylthiazolo-,l/-cyanine iodide One part of 2-methylthiazole was heated with '1.9 parts ot methyl p-toluenesulionate at 100 C.

tor half an hour. The 2methylthiazole methop-toluenesulfonate that was formed solidiied readily. This was dissolved in 18 parts o! absollute ethyl alcohol, 4.1 parts of nely pulverized 2- iodoquinoline ethiodide were added and the mixture brought-to boiling point under reflux. 1.4

parts oi' 85% caustic potash dissolved in 8 parts of hot absolute ethyl alcohol were then gradually added to the boiling suspension, and with good stirring. The liquid turned brownish and solid separated and the whole was refluxed for a further seven minutes. Thewhole was set aside to cool and the dye filtered olf, washed and purified by recrystallization from methyl alcohol. The

pure dye consists of brown crystals with a greenish reex and gives an orange solution in methyl alcohol.

I'he samedye was obtained whenthe 2.9 parts lof 2methylthiazole metho-p-toluenesulionate,

several times from methyl alcohol..

Exams: V

4-Meth1/l-1 ',3-diethylthiazol0-xl/-0Wnine iodide 2.7 parts of 2,4-dlmethylthiazole ethiodide were dissolved in 20 parts of absolute ethyl alcohol, 4.1 parts of 2-iodoquinoline ethiodide added, the whole brought to boiling and the condensation was carried out by adding a solution of 1.4 parts of'85% caustic potash dissolved in 12 parts of the solvent, refluxing for about .twenty minutes. After cooling the dye was illtered oil', washed and puried by recrystallization from methyl alcohol in which it gave an orange solution. The dye formed scarlet needles.

EXAMPLE VI 4Phenyl1,S-dimethylthiazolo-ip-cyanine iodide Two parts of 2-iodoquinoline methiodide, 1.6 parts of 4-phenyl-2-methylthiazole methiodide and 20 parts of methyl alcohol were boiled and a solution of 0.4 part of caustic soda dissolved in 24 parts of methyl alcohol added and the whole boiled under reilux for 15 minutes longer. After cooling the dye was filtered off, washed with water and recrystallized from methyl alcohol. Scarlet needles were obtained giving an orange solution.

This dye was also made by heating 2 parts and 1.6 parts of the two quaternary salts, in the order given above, with 10'parts of quinoline to 150 C. for ten minutes. The dye was isolated and puriiled as described for the dyein the second part of Example 1V.

A third method of making this dye is as i'ollows. The 2 parts and the 1.6 parts of the two quaternary salts, again taken in the same order, were refluxed with 30 parts oi' absolute ethyl alcohol and 1 part of triethylamine. Boiling was continued for ten minutes and the dye separated out during the course of the reaction. The whole was set aside to cool, the dye was ltered oir, washed and recrystallized from methyl 3.3 parts of 4-pheny1-2,5.dimethylthiazole methiodide were heated with 4.1 parts of 2- iodoquinoline ethiodide in 25 parts of quinoline at 13G-140 C. for fifteen minutes with agitation. During this time the salts dissolved and the liquid became a deep orange color. The liquid was allowedvto cool and the dye was precipitated by adding ether. 'Ihe dye rapidly crystallized on stirring, the ethereal layer was decanted and the dye filtered ofi'. The dye was washed and was recrystallized from methyl alcohol. It was thus obtained in the form of scarlet needles which gave an orange solution.

One and six tenths parts of 2,4-dimethylselenau zole were converted into the metho-p-toluenesulvifonate of the base by heating with 1.9 parts o1' methyl p-toluenesulfonate at C. for two hours. The solid product was well crushed and heated with 4 parts of 2-iodoquin`oline methiodide in 2i parts of quinoline for 15 minutes at 130- 140 C. After allowing the reaction mixture to cool, the dye was precipitated as a tar by mixing with ether and then the tar 'was stirred with aceand with water and purified by several recrystallizations from methyl alcohol, in which it gave an orange solution.

The dye was also made by dissolving the 3.5 parts of crude 2,4-dimethylselenazole, prepared as described above, in 20 parts of hot absolute ethyl alcohol, adding 4 parts of 2-iodoquino1ine methiodide, bringing the suspension to boiling and adding`a solution of 2 parts of triethylamine in 8 parts more of absolute ethyl alcohol. The dye rapidly separated from the boiling solution which was refluxed for a further 10 minutes. The dye was removed,.washed and crystallized from methyl alcohol, and was obtained in reddish-brown compact prisms and gave a deep orange solution in the solvent.

EXAMPLE IX y.

4 -M ethyl-1 ,3-diethylselenazolo-\p-cyanine iodide 1.6 parts of 2,4-dimethylselenazole were heated with 2 parts of ethyl p-toluenesulfonate at 100 C. for 20 hours and the crude quaternary salt was then heated with 4.1 parts of 2-iodoquinoline ethiodide and 20 parts of quinoline at 12o-130 C. for 15 minutes. The dye was subsequently deposited as a tar by adding ether to the cold reaction mixture and puried as described for the dye in Example VIII. It gave a deep orange solution in methyl alcohol, from which it crystallized in reddish-brown needles.

EXAMPLE X 1.1 parts of 4-phenyl-Z-methylselenazole was converted into the metho-p-toluenesulfonate by heating with 0.95 part of methyl p-toluenesulfonate for 12 hours at 100. The crude quaternary salt was dissolved in 20 parts of absolute ethyl alcohol, 2.05 parts of 2-iodoquinoline ethiodide added, the whole brought to boiling point and 1 part of triethylamine dissolved in 8 parts of absolute ethyl alcohol added gradually, with shaking. The whole was then refluxed a further 15 minutes, during which time the dye separated in crystalline form. After cooling the crystals were removed and recrystallized from methyl alcohol, and the dye was obtained in beautiful red needles which gave an orange solution in the solvent.

From the foregoing it will be apparent that these pseudo cyanines may be prepared from either the unsubstituted Z-methyl-oxazoles, -thiazoles, or -selenazoles, or from ones which have a substituent attached to either or both of the 4,5 carbon atms and that the nitrogen atoms of the two nuclei in the dye molecule may have similar or dissimilar groups attached thereto. The quinoline group may also be substituted or unsubstituted. While the presence or absence of these substituents or the particular character thereof may, affect the range of sensitization of these dyes or the ease or yield with which they are formed, their presence or absence does not aiect the general principles of my invention as the condensation is between the nuclei, the substituents not taking an active part in the condensation. Further, I do not restrict the operation of my process to a condensation occurring in the presence only of the specific condensing agents named, as equivalent strong organic or inorganic bases may be employed for the purpose as will be apparent to those skilled in the art, from reading the foregoing specification.

For instance, many other bases may be substituted for triethylamine which may be regarded as a typical strong organic base. For example, n-methylpiperidine and triethanolamine may be employed, the results with these two bases being quite good. vThese two bases are also tertiary bases, but I do not restrict myself to bases of this class, since diethylamine, which is a secondary base, may be employed. The primary base n-propylamine yields some of the dyes, as also does alcoholic ammonia and even aqueous ammonia, but the stronger tertiary bases are preferred. If one condensing agent is satisfactory for one particular condensation it does not follow that it will be equally satisfactory for all of 4the' others, but it is obvious to those skilled in this art that the most suitable condensing agent for any particular condensation may be selected from the variety of alkalis and bases hereindescribed. In general, triethylamine has been found to Work particularly Well.

The diagrammatic spectrograms constituting the accompanying drawing illustrate the regions of the spectrum to which the various types of dyes herein disclosed will sensitize a gelatinosilver-halide emulsion and the extent of the sensitization at various wave lengths. The gures of this drawing and the dye, the sensitizing properties of which each of the Figs. 1 to 7 illustrates, are listed, respectively, at the top of each spectrogram. These gures were all taken from silver bromide emulsions in which the respective dyes were incorporated as herein described; corresponding ones taken from chloride emulsions vary somewhat but are comparable in region and density.

In the preparation of emulsions containing these photographic sensitizers, it has been found that the dye may be dissolved in methyl alcohol and a volume of solution diluted with lwater and containing from 5 to 100 milligrams of dye added to 1000 cc. of, for instance, a flowable photographic gelatino-silver-halide emulsion, which may then be coated upon a suitable glass or cellulose derivative transparent support and allowed to dry, the details of which are Well known to emulsion experts. While it may not be necessary to add some of the sensitizers in a large amount, it may be necessary to add others in amounts larger than those given above; generally about 10 to 20 milligrams is sufcient to obtain the maximum sensitizing effect with a dye having good sensitizing power. The more powerful dyes, however, may require much less. The regulation or adoption of the most economical proportions will be apparent to those skilled in the art upon observing the sensitizing power of the particular dye for the particular emulsion in question. The above examples are, therefore, illustrative and not to be understood as limiting the invention in any sense, as it will be apparent that these dyes may be incorporated by other methods in many of the photographic emulsions customarily employed in the art, such for instance as by bathing the plate or film, upon .which the emulsion has been coated, in a solution of the dye in an appropriate solvent valthough this method of incorporating the dye in the emulsion is not to be preferred over that above described. Obviously, the claims are all intended to cover any combination of these dyes with a photographic emulsion whereby the dye exerts a sensitizing effect upon the emulsion.

A photographic emulsion in which is incorporated as above described, one or more of the 'contains a. pseudo cyanine salt having new dyes disclosed herein possesses in general strong sensitivity to the green and blue green portion of the spectrum.- Other variations and equivalents will doubtless occur to those skilled in this art, it being understood that theoregoing is intended only to illustrate to those skilled in the art how an oxazole, thiazole, or selenazole nucleus may be condensed with a quinoline nucleus to form highly useful and novel chemical compounds and how these new dyes may be utilized to sensitze photographic emulsions.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. A gelatine-silver-hal'ide Aemulsion which contains a pseudo cyanine salt having the iollowing structure in which R' and R2 represent alkyl groups, X represents an acid radical, A and B represent hydrogen, or alkyl groups, or aryl groups of the benzene series and Y equals oxygen, sulfur or selenium.

2. A gelatino-silver-halide emulsion 'which contains a pseudo cyanine salt having the Iollowing structure in which R' and R2 represent alkyl groups, X represents an acid radical, A and B represent hydrogen, or alkyl groups, or aryl groups of the benzene series.

3. A gelatino-silver-halide emulsion which the following structure in whichR' and R2 represent alkyl groups, X representss'an acid radical, A and B represent hydrogen. or alkyl groups. or aryl groups of the benzene series.

5. A gelatino-silver-halide emulsion which contains a l'-alkyl-3-alkyl-azolo-pseudo-cyanine salt in which the azole nucleus is selected from 'the group consisting o f oxazole, thiaxole and selenaaole.

6. A gelatino-silver-halide emulsion which con' tgliis a 1-alkyl-3-alkyl-oxazolo-pseudo-cyanine s 7. A gelatino-silver-halide emulsion which contains a 1'-alkyl-3-alkyl-thiazolo-pseudo-cyanine sa 8. A gelati'no-sil'ver-halide emulsion which contains a 1'-alkyl-3-alkyl-selenazolo-pseudo-cyanine salt.

' 9. A gelatino-silver-halide emulsion which contains a'pseudo-cyanine salt having the following structure :CH N l B/ \X in which R' vand R2 represent alkyl groups, X represents an acid radical, and B represents an alkyl group or an aryl group of the benzene series and Y equals oxygen, sulfur or selenium.

10. A gelatino-silver-halide emulsion which contains a pseudo-cyanine salt having the following structure EVN in which R' and R2 represent alkyl groups, X represents an acid radicaL'and Y equals oxygen, sulfur or selenium. i

12. A gelatina-silver-halide emulsion which contains a 4-phenyl-3-methyl-lf-ethyloxazolopseudo-cyanine salt.

13. A gelatine-silver-halide emulsion which contains a 3,4-dimethyl-1'ethylthiazolopseudo cyanine salt.

14. A. gelatine-silver-halide emulsion which contains a 4-phenyl-3methyl1ethylselenazolo pseudo-cyanine salt.

15. A photographic element comprising a supporting surface coated with a gelatno-silver-l halide emulsion which contains a pseudo-cyanine salt having the following structure in which R' and R24 represent alkyl groups, X represents an acid radical, A and B represent hydrogen, or alkyl groups, or aryl groups of the benzene series and Y equals oxygen, sulfur or selenium.

` LESUE G. B. BROOKER.

Certiiicate of Correction Patent No. 1,969,446. August 7, 1934.

A LESLIE G. s. BROOKER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 101, for the letters at the extreme right of the equation 2G-CH read 2O-0H3; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 4th day of September, A. D. 1934.

,[SEAL] R. SPENCER, p

Acting Oo'rlwnz'ssmwr of Patents. 

